This invention relates to thermal mass transfer donor elements for transferring materials to a receptor.
The thermal transfer of layers from a thermal transfer element to a receptor has been suggested for the preparation of a variety of products. Such products include, for example, color filters, spacers, black matrix layers, polarizers, printed circuit boards, displays (for example, liquid crystal and emissive displays), polarizers, z-axis conductors, and other items that can be formed by thermal transfer including, for example, those described in U.S. Pat. Nos. 5,156,938; 5,171,650; 5,244,770; 5,256,506; 5,387,496; 5,501,938; 5,521,035; 5,593,808; 5,605,780; 5,612,165; 5,622,795; 5,685,939; 5,691,114; 5,693,446; and 5,710,097 and International Publication Nos. WO 98/03346 and WO 97/15173, incorporated herein by reference.
For many of these products, resolution and edge sharpness are important factors in the manufacture of the product. Another factor is the size of the transferred portion of the thermal transfer element for a given amount of thermal energy. As an example, when lines or other shapes are transferred, the linewidth or diameter of the shape depends on the size of the resistive element or light beam used to pattern the thermal transfer element. The linewidth or diameter also depends on the ability of the thermal transfer element to transfer energy. Near the edges of the resistive element or light beam, the energy provided to the thermal transfer element may be reduced. Thermal transfer elements with better thermal conduction, less thermal loss, more sensitive transfer coatings, and/or better light-to-heat conversion typically produce larger linewidths or diameters. Thus, the linewidth or diameter can be a reflection of the efficiency of the thermal transfer element in performing the thermal transfer function.
One manner in which thermal transfer properties can be improved is by improvements in the formulation of the transfer layer material. For example, co-assigned U.S. patent application Ser. No. 09/392,386 discloses including a plasticizer in the transfer layer to improve transfer properties. Other ways to improve transfer fidelity during laser induced thermal transfer include increasing the laser power and/or fluence incident on the donor media. However, increasing laser power or fluence can lead to imaging defects, presumably caused in part by overheating of one or more layers in the donor media.
The present invention recognizes problems associated with trying to improve the sensitivity of thermal transfer and offers new approaches. The present invention provides improved constructions for thermal mass transfer donor elements, specifically providing new light-to-heat conversion layer (LTHC) constructions. The constructions and methods of the present invention can be used to provide thermal transfer donor elements that exhibit, for example, higher transfer sensitivity, fewer imaging defects (e.g., those defects related to donor element over-heating), and the like.
In one embodiment, the present invention provides a thermal mass transfer donor element that includes a thermal transfer layer and a light-to-heat conversion layer, wherein the light-to-heat conversion layer has at least two regions exhibiting different absorption coefficients. For example, the absorption coefficient can vary through the thickness of the light-to-heat conversion layer.
In another embodiment, the present invention provides a thermal mass transfer donor element that includes a thermal transfer layer and a non-homogeneous light-to-heat conversion layer, where the donor element is capable of being used for imagewise thermal mass transfer of material from the transfer layer to a receptor when the donor element is exposed to imaging radiation that can be absorbed and converted into heat by the non-homogeneous light-to-heat conversion layer. The non-homogeneous light-to-heat conversion layer is provided so that, for a set of imaging conditions, improved imaging properties can be attained (such as a lower maximum temperature, improved imaging sensitivity, increased imaging fidelity, and decreased imaging defect formation) compared to an otherwise nearly identical donor element that includes a homogeneous light-to-heat conversion layer that has a thickness and optical density that are the about same as for the non-homogeneous light-to-heat conversion layer.
In still another embodiment, the present invention provides a method for improving the imaging properties of thermal mass transfer donor media by providing a substrate and a thermal transfer layer, and then forming a light-to-heat conversion layer between the substrate and the thermal transfer layer, the light-to-heat conversion layer having at least two regions exhibiting different absorption coefficients.
In yet another embodiment, the present invention provides a method of thermal mass transfer including the steps of providing a donor element that includes providing a donor element that has a thermal transfer layer and a light-to-heat conversion layer, the light-to-heat conversion layer having at least two regions exhibiting different absorption coefficients; placing the thermal transfer layer of the donor element adjacent to a receptor substrate; and thermally transferring portions of the thermal transfer layer from the donor element to the receptor substrate by selectively irradiating the donor element.